From the Guidelines
When converting furosemide from oral to intravenous administration, the dose should be at least equivalent to the previous oral dose.
Key Points
- The initial intravenous dose of furosemide should be at least equal to the pre-existing oral dose used at home 1.
- For patients with new-onset acute heart failure or those without a history of renal failure and previous use of diuretics, an intravenous bolus of 20-40 mg may be considered 1.
- In cases where patients are already on chronic oral therapy, the intravenous dose should be at least equivalent to the oral dose 1.
- It's essential to tailor the intravenous diuretic dose to the type of acute heart failure and the patient's renal function, and to monitor urine output and renal function closely 1.
- The total furosemide dose should be limited to the smallest amount necessary to provide an adequate clinical effect, and should not exceed 100 mg in the first 6 hours and 240 mg during the first 24 hours 1.
From the FDA Drug Label
Adults: Parenteral therapy with Furosemide Injection should be used only in patients unable to take oral medication or in emergency situations and should be replaced with oral therapy as soon as practical. The usual initial dose of furosemide is 20 to 40 mg given as a single dose, injected intramuscularly or intravenously The dose may be raised by 20 mg and given not sooner than 2 hours after the previous dose until the desired diuretic effect has been obtained
The conversion for furosemide (Lasix) from oral (PO) to intravenous (IV) administration is 1:1. The same dose is used for both oral and intravenous administration, with the intravenous dose given slowly over 1 to 2 minutes. 2
From the Research
Conversion from Oral to Intravenous Administration
The conversion for furosemide (Lasix) from oral (PO) to intravenous (IV) administration can be determined based on the bioavailability of the drug.
- The mean absolute bioavailability of furosemide was found to be 42.8% and 44.0% as calculated from plasma and urine data, respectively 3.
- Another study reported a bioavailability of 51% for oral administration of furosemide in healthy subjects 4.
- A study in elderly patients found a mean bioavailability of 49% with a range of 12-112% 5.
Dosing Considerations
When converting from oral to IV administration, the dose may need to be adjusted based on the bioavailability of the drug.
- A study compared the efficacy and bioavailability of a 500 mg oral dose to a 250 mg IV dose in peritoneal dialysis patients 6.
- However, the exact conversion ratio is not explicitly stated in the provided studies.
Pharmacokinetics and Pharmacodynamics
The pharmacokinetics and pharmacodynamics of furosemide can affect its conversion from oral to IV administration.